Generally, in radar apparatuses, a electromagnetic wave is discharged and the reflection wave is received, therefore a target object (a ship or a buoy on the sea) is detected. Further, the detected target object is displayed on a display screen. Particularly for such a radar apparatus that is used in a transportation equipment that moves (rolls, pitches), such as a ship, in many cases, a fan beam type radar apparatus disclosed in JP3,559,236, which has directivity that is wide in a vertical direction so as to help capturing such a target object even with a disturbance of ship's movement (rolling, pitching) is adopted. In the fan beam type radar apparatus, a recognition of the target object is performed based on information on an amplitude of a non-modulated pulse signal.
Meanwhile, for example, JP2010-525336A discloses a radar apparatus installed on the ground that does not move (roll, pitch) like a ship and for highly accurately detecting a bird, which is equipped with a beam switching type antenna for repeating transmission and reception while switching an elevation angle at which a pencil beam is discharged for each pulse.
Generally, in a fan beam type radar apparatus, it has been difficult to discriminate a target object in a vertical direction. In addition, with the fan beam type, a signal intensity of a reception signal is obtained by integrating levels of the signal intensities in the vertical direction. Therefore, the influence of clutters that widely spread in a height direction, such as rain, is big and is a source of problem.
In order to discriminate a target object in the vertical direction (height) so as to solve the above problems, as disclosed in JP3,559,236 and JP2010-525336A, pulse signals corresponding to a resolution performance required for desired discrimination level in the vertical direction need to be repeatedly transceived. Thereby, the time for detecting a target object at each azimuth becomes longer as the number of the transceiving of the pulse signals increases, therefore, it is not suitable for a practical use, such as on a ship where monitoring in a wide range around an antenna is required.